Pump assemblies, for example heating circulation pump assemblies are known, which comprise a stator housing and a pump housing connected to the stator housing. A wet-running electric motor is arranged in the inside of the stator housing, i.e. the electric motor comprises a can or a canned pot, which is arranged between the rotor and the stator and seals the stator space with respect to the rotor space. Thereby, it known for the can at its axial end facing the pump housing to comprise a radially outwardly extending collar which in this region seals the stator housing at the interface to the pump housing, on the axial side. For this, it is known to arrange an annular shaped seal, for example a flat seal, between the pump housing and this collar. By way of this, one prevents fluid to be delivered, for example water, from penetrating outwards through the gap between the pump housing and the can.